Wintertime is associated with increased morbidity and mortality and a majority is related to cardiovascular causes, such as myocardial infarctions, heart failures, and strokes. It is also known, that both acute and long-term cold exposure increase blood pressure and cardiac workload, and this may contribute to the observed excess morbidity and mortality during the cold season.

Although the effects of cold on blood pressure are known among healthy people, these responses among risk groups, such as hypertensive people, are not established. In addition, changes in cardiac electrical activity or autonomic regulation are largely unknown. The cardiovascular responses in the cold could be different among hypertensive people because of disturbances in the circulatory regulation or function, such as aortic stiffening and increased vasomotor tone of peripheral arteries due to endothelial dysfunction associated with the disease. To assess this, a controlled experiment employing a cold exposure similar to everyday winter circumstances in a subarctic climate was performed.

The study assesses the blood pressure response of hypertensive and normotensive subjects to facial cooling. Blood pressure is measured before (warm, +18°C), during (cold, 15°C) and after (warm, +18°C) the employed cold exposure. The duration of each of these exposures are 30, 15 and 30 min.

The study participants were included according to a population based recruitment where a random sample of 1000 men (55-65 years old) living in Oulu, Finland was drawn from the Finnish Population Register. They were screened by telephone interviews for eligibility for the study. Eligible attendees measured their blood pressure home for a week according to the recommendations of the European Society of Hypertension and were classified either to hypertensive (systolic blood pressure ≥135 and/or diastolic blood pressure ≥85 mmHg) or normotensive (blood pressure <135/85mmHg). For the study we aimed at a 2:1 ratio of hypertensive and normotensive. The final study group consisted of 56 hypertensive and 35 normotensive middle-aged men.

Criteria

Inclusion Criteria:

Measured BP (home measurements of one week) above 135/85 mmHg were selected to the group of hypertensive subjects.

Those with BP below 135/85 mmHg were selected as controls.

Exclusion Criteria:

Presence of coronary heart disease, respiratory diseases, and the use of antihypertensive drug treatment.

an average home BP ≥175/105 mmHg, initiating antihypertensive drug treatment, failed home BP measurements, and having a respiratory infection within a week prior to the controlled measurements

Contacts and Locations

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study.
To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below.
For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT02007031